A. Technical Field
The present invention relates to a cyclic imino ether group containing polymer and a production process therefor.
B. Background Art
Cyclic imino ether group containing polymers, as formed by introducing cyclic imino ether groups, such as oxazoline group, into part of side chains of polymers, such as polystyrene, poly(styrene-acrylonitrile), and poly(methyl methacrylate), are in practical use, for example, as high-molecular crosslinking agents and high-molecular compatibilizers, by utilizing high reactivity of the cyclic imino ether group.
The cyclic imino ether group containing polymer is mainly produced by a process including the step of radical-polymerizing a cyclic imino ether group containing monomer and other monomers. Solution polymerization gives the cyclic imino ether group containing polymer in a dissolved state, and suspension polymerization gives the cyclic imino ether group containing polymer in a dispersed state. Therefore, there is need to separate, thereby, remove, volatile components, such as solvents, unreacted monomers, and volatile by-products, from these states. For example, there are proposed processes in which: the reaction liquid containing the polymer resultant from the polymerization is added to a solvent which dissolves volatile components, but does not dissolve the polymer, thus extracting the volatile components to remove them (JP-A-162616/1983); the volatile components are evaporated with a flash evaporator, and the polymer as left behind is extracted in a melted state (JP-A-276807/1986, JP-A-129334/1987, and JP-A-205411/1991); the volatile components are removed by supplying the reaction liquid containing the polymer, resultant from the polymerization, to a screw type devolatilizing extruder directly or after preheat-drying the reaction liquid, (JP-A-126411/1984, JP-A-058006/1984, JP-A-135814/1982, JP-A-040687/1975, JP-A-040688/1975, JP-A-049603/1982, JP-A-147501 /1988, and JP-A-049925/1991).
Some of the above processes are practically employed as industrial processes as well, and it has so far been thought that the amount of volatile components could sufficiently be reduced by those processes to such an extent that there is practically no problem. Such a thought was caused by that when the amount of volatile components was extremely small there was no means to quantify it, and further by that the recognition or regulation to the amount of residual volatile components were therefore looser than the current ones.
However, in recent years, environmental problems are being regarded as more and more important, and further, means for analysis have advanced so much as to enable even the quantification of a small amount of residue which has so far been "below the detection limit." Thus, cases where the conventional amount of residue is regarded as a problem have got to occur. As to cyclic imino ether group containing monomers having particularly strong toxicity among the volatile components, more reduction of the amount of the residue thereof has got to be demanded.